AN821 Datasheet, PDF (1/4 Pages) STMicroelectronics – NEW LAYOUT INSULATION REQUIREMENT

AN821
APPLICATION NOTE
NEW LAYOUT INSULATION REQUIREMENT
INTRODUCTION
In order to assume better level of security for telecommunication system users, some new rules have been
published. This is the case of the IEC950 standard which dedicates one chapter to this subject. This kind
of requirement is beginning to be active in Germany for example.
REQUIREMENT
Figure 1 shows the principle of the test circuit. The test consists of the insulation measurement of the tele-
communication network and the earth. During this test it is permitted to remove components. In fact in the
field the procedure is done as follow:
– The protection device is removed from the board.
– The telecommunication lines are connected together. Tip and Ring lines from all the subscribers for an
exchange equipment, or A and B lines for a telephone set.
– A voltage of 2 kV is applied between the lines and ground.
– The current flowing in the test circuit shall not exceed the requested limit, for example 10 mA in the
IEC950 case.
Figure 1. Test Circuit
mA
TEST
GENERATOR
TELECOM. EQUIPMENT
May 2004
REV. 2
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